1. Field of the Invention
This invention generally pertains to a machine for mechanically ejecting selected items from a stream of products. More particularly this invention pertains to sorting machines that separate substandard items from standard items, the items passing through the machine in large volumes at high rates of speed.
2. Description of the Prior Art
A typical machine of the type envisioned for application of the present invention is a high speed sorting machine typically used for sorting fungible products in the food industry or otherwise. For example, individual tomatoes are caused to flow in front of an optical detector in such a machine to separate "substandard" items from standard product. The term "substandard" can apply to a tomato having undesirable characteristics or to unwanted items such as dirt clots, stems, and leaves. For instance, green tomatoes can be removed from a batch of tomatoes that are primarily red in color, or vice versa. The term may apply to product colors or different lengths or other qualities that are perfectly acceptable in the abstract, but are not within the standard limits of quality established for acceptable standard products for particular sorting.
The commonly employed sorting mechanism used in today's sorting machines is the optical sensor. Sensors include one or more photodetectors, such as photo diodes that are sensitive not only to black, white and shades of gray differences, but also to subtle variation in color hues. Also, many such sensors, including the entire sensor combination of parts, also are capable of discriminating against different sizes of products. All of the machines of the general class fitting the above description have in common a protective, light emitting window for the sensor or sensors to protect the sensors from contamination. In some cases, the window may protect only one sensor element, but in many cases, it is common that the housing enclose a plurality of sensors that are spaced about an opening through which the stream of product to be sorted is directed.
In order to pass the product in front of the window, many such systems utilize a dual conveyor belt system. Product enters the system on an incoming belt with the end of the belt positioned above the window such that when the product drops off the end it falls in front of the window on to a lower conveyor belt located beneath the window. The sensor determines whether the product in front of the window is substandard or standard.
Such machines also include an ejector located downstream from each sensor that is actuated by an electrical signal originating from sensor detection. When a substandard product is detected, an electrical actuating signal is produced and the ejector is actuated just as the substandard product and the ejector are in alignment. Therefore, there is a delay between detection and ejection, but it is ever so slight because the further the ejector is from the detector, the more substandard product can escape by being diverted or hit by other product in the product stream. Thus, the ejector is normally located as close as possible to the sensor or sensors, ideally being just downstream therefrom and closely adjacent thereto.
The ejector mechanism can be a compressed air ejector when sorting smaller sized fungible product. However, when sorting larger fungible products such as tomatoes or potatoes, mechanical ejector mechanisms are almost universally used. That is, when the substandard product arrives opposite the ejector, the ejector is moved into physical contact with the substandard product forcing it out of the standard product stream. A typical ejector includes an ejector finger which is forced into the product stream to remove detected substandard products by an actuating means, such as that shown in U.S. Pat. No. 4,260,062 issued to Lockett and assigned to the assignee of the present invention. The ejector finger is actuated by a pneumatic valve having a pneumatic cylinder rigidly mounted to a stationary frame, wherein the finger is pivotally connected to the frame, a connection stationary relative to the product stream and pivotally connected to the rod of the cylinder, and a connection movable relative to the product stream. Upon receipt from the electrical actuating signal from the sensor, the valve is activated, thereby extending the cylinder rod and extending the finger into the product stream. This is done with such speed and accuracy that substandard products can be removed from the product stream, while standard products are allowed to continue undisturbed in the "good" product stream. The ejection cycle can occur in excess of 1/30th a second.
An ejector finger of the type described above includes an elongate contactor pivotally connected to the frame by a pin and bushing. The contactor is also pivotally connected to the cylinder rod by a second pin and bushing. Although this type of ejector finger is presently being used to sort products effectively, the life span of a finger is short relative to the life span expectancy of a sorting machine. This short life span is due to the wear on the pivot points. The wear is primarily caused by a combination of environmental effects, including, mud, dust, dirt and small bits of product, the speed of an ejection cycle, and the number of ejection cycles the finger undergoes during the lifetime of the machine. Typically, an ejector finger may be cycled as many times as three (3) million cycles in a three month period, which represent the approximate time of a harvesting season. In most cases, the ejector finger will not last the duration of a harvesting season and require replacement. Most of the industrial sorters include a plurality of fingers associated with each of a plurality of sensors. Replacing these fingers prior to the end of a harvesting season is a very costly and time consuming process, not to mention, an inconvenience during the most active time of the machine's use.
Another problem associated with the ejector described above is due to the mechanism mounting the ejector to the sorting machine frame. Typically the tail end of the pneumatic cylinder is supplied with a mounting plate for connecting to a clevis and pin. The clevis is then rigidly bolted or rivetted to the frame of the sorting machine. This rigid mounting mechanism undergoes significant amount of stress during a harvest season and many times requires replacement. The clevis pin arrangement is typically very expensive.
In an attempt to design an ejector that will last the duration of a harvest season without requiring replacement, the assignee of the present invention developed a new ejector finger described in U.S. Pat. No. 5,279,426. The ejector finger described in this patent is of a monolithic structure and of homogeneous material. Thus, the pins and bushing of the ejector finger mentioned above and thus, the wear points, have been replaced by hinges of reduced dimensions eliminating the wear due to the combination of environmental effects, including mud, dust, dirt, and small bits of product. Even though the life span of this new finger is longer than that of the ejector finger described above, some fingers still do not last the duration of the harvest season.
Therefore, it is a feature of the present invention to provide an improved sorting machine including a mechanical ejecting separation of substandard products, from a stream of products wherein the mechanical ejector mechanism will function at least through the duration of a harvest season.
It is another feature of the present invention to provide an improved mechanical ejector for separating substandard products from a stream of products passing through a sorting machine, wherein the mechanical ejector is less susceptible to the environmental conditions than prior art ejectors to thereby enhance the life span of the ejector.
It is yet another feature of the present invention to provide an improved less expensive and easily replaceable mechanical ejector for separating substandard products from a stream of products passing through a sorting machine.